Field of the Invention
Embodiments disclosed herein relate to electro-chromic films and methods and applications thereof.
Background
Electro-chromic (EC) film stacks may be applied to surfaces when it is desirable to change the optical transmission properties of the surface. For example, the stacks may be applied to ophthalmic lenses to reduce transmission of harmful ultra-violet light through the lenses. An electro-chromic film stack generally comprises at least one electro-chromic layer in contact with at least one ion conductor layer. When a voltage is applied, ions and electrons are transferred between the different layers, resulting in a change of the optical properties of the stack. When the voltage is turned off, the stack's optical properties return to the unaltered state.
Despite the large number of on-going research studies in the field of various EC technologies, there is still a need of compact and mechanically-robust solid-state electro-chromic film stack, which can be easily applied on existing ophthalmic lens blanks, semi-finished blanks (SFB), or other surfaces that need controllable variable transmission performance. It may also be desirable for such EC stack to operate under lower voltage, and thus, not require large, heavy and aesthetically non-acceptable batteries. In addition, the variable-transmission EC stack should be first-responding with a satisfactory dynamic range compared to the current available photochromic lenses and other switching technologies. Moreover, such robust EC stack has a potential to be applied to any other large area transparent surfaces. These include but are not limited to architectural windows, glass roofs, car windshields, and other applications that require controllable transmission for energy-saving and other purposes.
The EC film stack should also survive all post-processing steps of the surfaces that it is applied to. For instance, if applied to ophthalmic SFBs, it should survive the surfacing to different lens prescriptions, edging into different lens shapes and grooving steps, which is not the case with non-solid EC devices utilizing liquid electrolytes. Furthermore, if the solid EC film stack can be deposited on a single substrate, it would be very beneficial for the reduction the “bulkiness” of the final product such as but not limited to ophthalmic lens, motorcycle helmets, and windows.